Leinster head coach Leo Cullen admitted the final 20 minutes of his side's Champions Cup final victory were "torturous" as he praised his players' resilience.

Cullen became the first man to win the tournament as a player and a coach as Isa Nacewa's 79th-minute penalty secured a 15-12 defeat of Racing 92 in Bilbao and a record-equalling fourth European Cup triumph.

Reflecting on the try-less encounter, head coach Cullen said: "They played that territory game and just made it very difficult for us.

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Racing 92 fly-half Remi Tales missed a late drop-goal as Leinster clung on to claim a 15-12 victory in the Champions Cup final in Bilbao.

"There were times in the first half when we were carrying into heavy traffic and then there's players on our side of the ball.

"We just couldn't get a flow into the game and it was frustrating at times. We didn't quite execute a couple of things and we were just a little bit off.

"The message was very clear at half-time [at 6-6] -- just stay patient. We couldn't quite get our noses in front, Racing always had that bit of an edge, in terms of they were always on the right side of that three points.

"But credit to the players, it's phenomenal how they dug it out, stayed very composed right to the very end and pushed and pushed and pushed the whole time."

He added: "It wasn't pretty at times, it was tough to watch that last 20 minutes. Torturous in many ways. Maybe the fact that it was ugly like that makes it even better.

"The quarterfinal and semifinal [against Saracens and Scarlets] were some very, very good performances from the team, and it was a completely different type of performance today."

Racing scrum-half Teddy Iribaren -- kicking in the injury-enforced absence of Maxime Machenaud, Pat Lambie and Dan Carter -- was only a couple of minutes away from steering the French club to their first European title.

However, Leinster's retiring skipper Nacewa, 35, landed a penalty to have the final say.

Sexton, now a fellow four-time European Cup champion like Nacewa, admitted afterwards: "It was great for Isa to finish off with the last couple of penalties.

"I just slipped during the game and tweaked my groin a bit, and I was struggling a little bit with it. There was no point risking it.

"Obviously when you have such a good kicker like him beside you, you just hand it over to him, and he did the job."

Nacewa, who will retire in the summer, is hopeful that the young guns can keep Leinster challenging for top honours.

"It's a special day for Leinster Rugby and the whole province. A lot of work goes unnoticed...back-office staff, backroom staff, coaches, players who weren't involved today," he said.

"There's a solid core group of guys there, minus me, who will be pushing on for higher honours after this. It's good to be in such good shape as a club going forward."

Meanwhile, a second European final defeat in three seasons was tough to take for Racing skipper Yannick Nyanga.

Nyanga, who confirmed that he is retiring at the end of the season, said: "I would have liked to finish my last European Cup match in another way.

"I'm still proud to have been captain of this team. There are lessons that are harder to learn than others and this is part of it."